A macro cell base station apparatus for wireless communication (macro base station) having a large cell radius is provided mainly outdoors, and, in addition to this, 3rd Generation Partnership Project (3GPP) is studying to provide a femto cell base station apparatus (femto base station) having a cell radius of approximately several tens of meters in a household, office, and an indoor facility such as a restaurant.
FIG. 1 shows a system configuration in the event a femto base station is provided in a household. As shown in FIG. 1, in a household, it is likely that, in addition to a femto base station, an IP telephone, an IP-TV, and furthermore a plurality of personal computers and suchlike devices, share one xDSL, FTTH or suchlike Internet-connecting network via fixed-line system. The femto base station is connected with a core network via a concentrator (GW).
Lately, to provide a solution for increasing traffic of, for example, data communication, many mobile operators are forced to improve equipment and facilities. Consequently, by introducing a femto base station, it is possible to keep the cost lower than providing additional base stations outdoors and off-load indoor-originated communication traffic directly to the Internet. By this means, it is expected to reduce load of a core network in a mobile network system. Also, in future, a communication device in a user's premise and a mobile terminal are expected to be able to communicate directly each other, via a femto base station, without traversing mobile operator's core network, and provide various interactive services to the user.
Next, the steps of call connection establishment in an IMT-2000 packet system, disclosed in non-patent literature 1 for example, will be described using FIG. 2. Referring to FIG. 2, a UE, after a connection established with a Radio Network Controller (RNC) through Radio Resource Control (RRC) call connection establishment procedure (ST 11), requests a start of service to an SGSN, using a service request, which is a CPRS Mobility Management (GMM) protocol signal (ST 12). A service request message includes information to request a signaling connection (connection for signaling) between the UE and the SGSN (service type: signaling).
The SGSN performs authentication processing for the UE having requested signaling connection (ST 13), and, if, as a result of this, the UE is identified as a valid UE, indicates RNC to initiate ciphering processing for a radio connection by a security mode command, which is an RANAP signal (ST 14). Then, if ciphering processing has been performed successfully, the UE requests call connection establishment using a PDP context activation request (or “Activate Packet Data Protocol Context Request”), which is a Session Management (SM) signal (ST 15).
In this SM signal, an Access Point Name (APN) to specify a target data network (packet data network: PDN) for the connection is provided, so that the SGSN, upon receiving this SM signal, acquires IP address information of the GGSN to connect to, based on the APN information, through a Domain Name System (DNS) procedure. Then, upon successfully acquiring the IP address of the GGSN, the SGSN transmits an RAB Assignment Request, which is an RANAP signal, to the RNC, and requests tunnel establishment between the RNC and the SGSN (ST 16).
Next, the SGSN, having checked the tunnel established between the RNC and the SGSN, transmits a PDP context creating request (or “Create PDP Context Request”), which is a GPRS Tunneling Protocol (GTP) signal, to the GGSN having the IP address acquired through the DNS procedure, and requests call connection establishment for the UE (ST 17).
In this GTP signal, also, APN information is provided, so that GGSN having received the GTP signal can identify the PDN to establish the connection, based on the APN information. When the GGSN successfully completes call connection establishment processing, the SGSN is reported that call connection establishment processing has been performed successfully, by means of a PDP context creating response (or “Create PDP Context Response”), which is a GTP signal (ST 18). At this point in time the GGSN configures routing information (i.e. route selection) for the UE, and manages the routing information as PDP context.
Next, a response signal from the GGSN is transmitted to the UE using a PDP context activation accept (or “Activate PDP Context Accept”), which is an SM signal (ST 19), and the UE starts transmitting and receiving user data (i.e. packet communication) (ST 20). At this point in time, the SGSN configures routing information for the UE, and manages the routing information as PDP context.
With this way, through the above series of processing, an IMT-2000 packet system sets up logical connections between a UE and a GGSN on a per connection basis and performs tunneling, thereby enabling packet communication.
Next, the steps of traffic off-loading for communication traffic between a femto base station and the Internet or home network, without traversing mobile operator's core network, will be described using FIG. 3. Note that, parts in FIG. 3 that are the same as in FIG. 2 will be assigned the same reference codes as in FIG. 2, and their detailed descriptions will be omitted. Assume here that the femto base station has the SGSN and GGSN functionalities shown in FIG. 2. Also, since the UE cannot be attached to more than one SGSN at same time, another assumption is given that the UE keeps being attached to one SGSN that is located in a core network.
The femto base station, having received a PDP context activation request transmitted from the UE, does not transfer this request to the SGSN, and, instead, selects an PDN to connect to, based on APN information, using its own SGSN function (ST 21). Assume that, for example, the ISP to provide broadband access to the use's home can be identified based on information included in APN.
The femto base station determines to process call connection establishment for the UE using its co-located GGSN function which the femto base station owns. Later, by performing processing from ST 16 to ST 20 in FIG. 2 using the GGSN, SGSN, RNC and Node B functionalities provided in the femto base station make it possible to establish logical connections between the UE and the GGSN, on a per connection basis, and consequently enable communication traffic originating from a femto base station to be off-loaded directly to the Internet or home network, without traversing a mobile operator's core network.